EP1096719A2 - Verfahren und System zur Relaisdatenwiederübertragung - Google Patents

Verfahren und System zur Relaisdatenwiederübertragung Download PDF

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Publication number
EP1096719A2
EP1096719A2 EP00123380A EP00123380A EP1096719A2 EP 1096719 A2 EP1096719 A2 EP 1096719A2 EP 00123380 A EP00123380 A EP 00123380A EP 00123380 A EP00123380 A EP 00123380A EP 1096719 A2 EP1096719 A2 EP 1096719A2
Authority
EP
European Patent Office
Prior art keywords
frame
transmission
data
transmitter
relay
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00123380A
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English (en)
French (fr)
Other versions
EP1096719A3 (de
Inventor
Koji Ikeda
Akio Kurobe
Go Kuroda
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Panasonic Corp
Original Assignee
Matsushita Electric Industrial Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Matsushita Electric Industrial Co Ltd filed Critical Matsushita Electric Industrial Co Ltd
Publication of EP1096719A2 publication Critical patent/EP1096719A2/de
Publication of EP1096719A3 publication Critical patent/EP1096719A3/de
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/14—Two-way operation using the same type of signal, i.e. duplex
    • H04L5/16—Half-duplex systems; Simplex/duplex switching; Transmission of break signals non-automatically inverting the direction of transmission
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
    • H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
    • H04B7/2643—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile using time-division multiple access [TDMA]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1809—Selective-repeat protocols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L2001/0092—Error control systems characterised by the topology of the transmission link
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
    • H04L69/30—Definitions, standards or architectural aspects of layered protocol stacks
    • H04L69/32—Architecture of open systems interconnection [OSI] 7-layer type protocol stacks, e.g. the interfaces between the data link level and the physical level
    • H04L69/322—Intralayer communication protocols among peer entities or protocol data unit [PDU] definitions
    • H04L69/324—Intralayer communication protocols among peer entities or protocol data unit [PDU] definitions in the data link layer [OSI layer 2], e.g. HDLC

Definitions

  • the present invention relates to methods and systems for relay transmission utilizing a relay transmitter located between data transmitters on the transmission and reception sides and, more specifically, to a method and a system for relay transmission in which data transmission is not done concurrent with data reception.
  • FIG. 15 is a diagram showing the structure of a data transmission system in the above conventional technology.
  • the data transmission system includes a data terminal 1521 where data is generated, a data transmitter on the transmission side 1511 for transmitting the received data in the form of packet, a relay transmitter 1512 for receiving the packet data from the data transmitter on the transmission side 1511 via a low-orbit satellite circuit 1503, a relay transmitter 1513 for receiving the packet data from the relay transmitter 1512 via a stationary-satellite circuit 1504, a data transmitter on the reception side 1514 for receiving the packet data from the relay transmitter 1513 via a radio circuit 1505 being a cellular network, and a data terminal 1522 for receiving the data from the data transmitter on the reception side 1514 for data processing.
  • the data transmitted from the data terminal 1521 is provided with an error detection code by the data transmitter on the transmission side 1511 for transmission in the form of packet.
  • the data packet is relayed via the relay transmitters 1512 and 1513 to the data transmitter on the reception side 1514.
  • the relay transmitter transmits a retransmission request to the transmitter preceding thereto.
  • the requested transmitter then retransmits a packet identical to the disappeared.
  • a radio wave emitted by a transmitter for radio transmission is generally intense but received is weak as came across the long distance. Consequently, the radio wave during transmission interferes with that during reception, rendering data reception difficult.
  • This is an exemplary near-far problem.
  • a transmission channel and a reception channel are close in frequency to each other in such case, interference therebetween is increased due to leakage of signal component from the transmission channel, rendering data reception more difficult. If those channels are equal in frequency, needless to say, the difficulty for data reception gets considerably high.
  • transmitting the retransmission request in the conventional data transmission system may affect data transmission on other data links, resulting in transmission failure.
  • required is a carefully designed circuit for assuredly receiving data, although leading to high cost and another effort to design and manufacture a device equipped with such circuit.
  • each transmitter with only one radio modem is effective.
  • the radio modem is functionally incapable of simultaneously perform data transmission and reception even in the different frequencies, and switching between the frequencies must be concurrently done. Consequently, if those transmitters share the same frequency of channel, the retransmission request transmitted in the conventional manner may collide with data being transmitted on other data links, resulting in transmission failure. Even if the transmitters do not share the same frequency of channel, the radio modems should be switched between frequencies with appropriate timing, otherwise failed in relay.
  • an object of the present invention is to provide a method and a system for relay transmission being free from data collision with a transmission request on data links and accordingly causing no failure in relay.
  • the present invention has the following features to attain the object above.
  • a first aspect of the present invention is directed to a relay transmission method for not-concurrently performing data transmission and reception, and sequentially transmitting a data frame from a transmitter on the transmission side to a transmitter on the reception side via one or more relay transmitters, the method comprising:
  • the number of data frames retransmitted from the transmission on the transmission side can be reduced, thereby shortening time for retransmission and thus increasing the efficiency of retransmission.
  • any wasteful retransmission request is prevented.
  • a directional antenna is used and changed its direction depending on from which data comes.
  • a relay transmitter by radio can be directionally set for transmission/reception so that multipath fading can be prevented.
  • the antenna can be adjusted to be ready for next transmission frame without waiting, i.e., no longer than required, for transmission frames which have not transmitted due to some error. Therefore, data transfer can be assuredly achieved.
  • a directional antenna is used and changed its direction depending on from which data comes.
  • a relay transmitter by radio can be directionally set for transmission/reception so that multipath fading can be efficiently prevented.
  • each different frequency channel is available for transmitters. Therefore, even if any disturbance wave source is observed in the vicinity of the transmitters, and even if such source has each different frequency characteristics, the transmitters can be in each appropriate frequency channel. Accordingly, a throughput can be increased.
  • a throughput can be maximized by selecting the frequency channel appropriately for each communications section.
  • each transmitter can know a time left for transfer on the path, preventing data transfer from being carried out after a transfer valid period.
  • the efficiency of data transfer can be improved by reducing an area of the transfer valid period information added to the transmission frame.
  • a directional antenna is used and changed its direction depending on from which data comes.
  • a relay transmitter by radio can be directionally set for transmission/reception so that multipath fading can be prevented.
  • the antenna can be adjusted to be ready for next transmission frame without waiting, i.e., no longer than required, for transmission frames which have not transmitted due to some error. Therefore, data transfer can be assuredly achieved.
  • a predetermined frequency channel is initially selected among plural
  • each different frequency channel is available for transmitters. Therefore, even if any disturbance wave source is observed in the vicinity of the transmitters, and even if such source has each different frequency characteristics, the transmitters can be in each appropriate frequency channel. Accordingly, a throughput can be increased. Further, the frequency channel can be set to be ready for next transmission frame without waiting, i.e., no longer than required, for transmission frames which have not transmitted due to some error. Therefore, data transfer can be assuredly achieved.
  • data collision can be successfully prevented, especially data collision often observed between a current transmission and the following transmission when data transmission is repeated with a predetermined intervals to attain a constant throughput. This is occurred because the number of retransmission cannot be specified depending on in which state the transmission path is.
  • a manner to calculate the maximum length of time taken for retransmission in the twelfth aspect is typically specified.
  • the transmitter on the reception side can easily determine whether to transmit a retransmission request. Further, data collision can be prevented between a current transmission and the following transmission. Still further, the calculation done in the transmitter on the reception side can be simplified.
  • a fourteenth aspect of the present invention is directed to a relay transmission system for non-concurrently performing data transmission and reception, and sequentially transmitting a data frame from a transmitter on the transmission side to a transmitter on the reception side via one or more relay transmitters,
  • the number of data frames retransmitted from the transmission on the transmission side can be reduced, thereby shortening time for retransmission and thus increasing the efficiency of retransmission.
  • a directional antenna is used and changed its direction depending on from which data comes.
  • a relay transmitter by radio can be directionally set for transmission/reception so that multipath fading can be prevented.
  • the antenna can be adjusted to be ready for next transmission frame without waiting, i.e., no longer than required, for transmission frames which have not transmitted due to some error. Therefore, data transfer can be assuredly achieved.
  • a directional antenna is used and changed its direction depending on from which data comes.
  • a relay transmitter by radio can be directionally set for transmission/reception so that multipath fading can be efficiently prevented.
  • each different frequency channel is available for transmitters. Therefore, even if any disturbance wave source is observed in the vicinity of the transmitters, and even if such source has each different frequency characteristics, the transmitters can be in each appropriate frequency channel. Accordingly, a throughput can be increased. Further, the frequency channel can be set to be ready for next transmission frame without waiting, i.e., no longer than required, for transmission frames which have not transmitted due to some error. Therefore, data transfer can be assuredly achieved.
  • the transmitter on the transmission side further comprises:
  • each transmitter can know a time left for transfer on the path, preventing data transfer from being carried out after a transfer valid period.
  • a directional antenna is used and changed its direction depending on from which data comes.
  • a relay transmitter by radio can be directionally set for transmission/reception so that multipath fading can be prevented.
  • the antenna can be adjusted to be ready for next transmission frame without waiting, i.e., no longer than required, for transmission frames which have not transmitted due to some error. Therefore, data transfer can be assuredly achieved.
  • each different frequency channel is available for transmitters. Therefore, even if any disturbance wave source is observed in the vicinity of the transmitters, and even if such source has each different frequency characteristics, the transmitters can be in each appropriate frequency channel. Accordingly, a throughput can be increased. Further, the frequency channel can be set to be ready for next transmission frame without waiting, i.e., no longer than required, for transmission frames which have not transmitted due to some error. Therefore, data transfer can be assuredly achieved.
  • a twenty-third aspect of the present invention is directed to a transmitter on the transmission side for non-concurrently performing data transmission and reception, and sequentially transmitting a data frame to a transmitter on the reception side via one or more relay transmitters, comprising:
  • the number of data frames retransmitted from the transmission on the transmission side can be reduced, thereby shortening time for retransmission and thus increasing the efficiency of retransmission.
  • a twenty-fifth aspect of the present invention is directed to a transmitter on the reception side for non-concurrently performing data transmission and reception, and sequentially transmitting a data frame to a transmitter on the transmission side via one or more relay transmitters, comprising:
  • the number of data frames retransmitted from the transmission on the transmission side can be reduced, thereby shortening time for retransmission and thus increasing the efficiency of retransmission.
  • a twenty-seventh aspect of the present invention is directed to one or more relay transmitters for non-concurrently performing data transmission and reception, and sequentially transmitting a data frame from a transmitter on the transmission side to a transmitter on the reception side, each comprising:
  • the number of data frames retransmitted from the transmission on the transmission side can be reduced, thereby shortening time for retransmission and thus increasing the efficiency of retransmission.
  • FIGS. 1 to 3 are diagrams showing the structure of a data transmission system according to a first embodiment of the present invention.
  • FIG. 1 shows the structure of a relay transmitter 10 located between transmitters on the transmission and reception sides 30 and 20 for increasing the distance for data transmission
  • FIG. 2 the structure of the transmitter on the reception side 20 for receiving data transmitted from the transmitter on the transmission side 30,
  • FIG. 3 the structure of the data transmitter on the transmission side 30.
  • the transmitter on the reception side 20, transmitter on the transmission side 30, and relay transmitter 10 are connected to one another via transmission paths 40.
  • Each of such devices is structurally and operationally described next below.
  • the relay transmitter 10 is provided with a data reception part 101 for demodulating a transmission wave on the transmission path 40 so as to generate a transmission frame including polling frame, retransmission request frame, data frame, and the like, an error detection part 102 for detecting any error in the transmission frame using an error detection code added to the transmission frame, a frame header analysis part 103 for analyzing the transmission frame for its frame type and destination address, a relay controller 104 for controlling other parts, a retransmission frame buffer 105 for accumulating a to-be-retransmitted transmission frame, a relay buffer 106 for accumulating the transmission frame at relay, a destination address change part 107 for rewriting the destination address in the transmission frame, an error detection code addition part 108 for calculating and rewriting the error detection code in the transmission frame, a data transmission part 109 for modulating the transmission frame for send-out onto the transmission path as another transmission wave, and a retransmission request frame reconstruction part 110 for changing a frame number in a retransmission request frame
  • the data reception and transmission parts 101 and 109 are typically in a single modem 100, resulting in no simultaneous data transmission and reception. Here, there no need to put those in the same modem as long as simultaneous data transmission and reception is prevented. This is for avoiding the above-described near-far problem and interference between adjoining channels, for example.
  • the data reception part 101 receives a transmission frame.
  • the received transmission frame is determined as being normal or not by the error detection part 102. If any error is detected in the frame, the error detection part 102 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 103.
  • the frame header analysis part 103 informs the relay control part 104.
  • the relay control part 104 clears the retransmission frame buffer 105 and the relay buffer 106.
  • the frame header analysis part 103 also outputs the analyzed frame to the destination address change part 107.
  • the destination address change part 107 rewrites the frame to address to the transmitter on the transmission side, and then outputs the frame to the error detection code addition part 108.
  • the frame is provided with an error detection code, and outputted out of the data transmission part 109.
  • the frame header analysis part 103 informs the relay control part 104.
  • the frame header analysis part 103 also outputs the analyzed frame to the destination address change part 107.
  • the destination address change part 107 rewrites the frame to address to the transmitter on the reception side, and then outputs the frame to the error detection code addition part 108.
  • the frame is provided with an error detection code, and accumulated in the retransmission frame buffer 105.
  • the frame is also stored in the relay buffer 106.
  • the relay control part 104 controls, if detected reception of a series of data frames having been completed, data stored in the relay buffer 106 to be transmitted out of the data transmission part 109, and then clears the relay buffer 106.
  • the frame header analysis part 103 informs the relay control part 104.
  • the retransmission request frame also goes to the retransmission request frame reconstruction part 110.
  • the relay control part 104 clears the relay buffer 106, and then determines whether the retransmission frame buffer part 105 has every data frame requested for retransmission. If every data frame is found therein, the data frame(s) is stored in the relay buffer 106.
  • the relay control part 104 also informs the retransmission request frame reconstruction part 110 of the data frame(s) by frame number not found In the retransmission frame buffer 105.
  • the retransmission request frame reconstruction part 110 removes, out of the retransmission request frame, any frame number(s) already stored in the retransmission frame buffer 105, and forwards the retransmission request frame to the destination address change part 107.
  • the destination address change part 107 rewrites the retransmission request frame to address to the transmitter on the transmission side, and then outputs the frame to the error detection code addition part 108.
  • the retransmission request frame is provided with an error detection code, and transmitted out of the data transmission part 109.
  • the transmitter on the reception side 20 is provided with a polling period count part 201 for counting time, and forwarding a command of polling transmission at predetermined intervals, a polling frame generation part 202 for generating a polling frame, an error detection code addition part 203 for calculating an error detection code and adding that to the transmission frame, a data transmission part 204 for modulating the transmission frame for send-out onto a transmission path as a transmission wave, a data reception part 205 for demodulating the transmission wave on the transmission path so as to generate a transmission frame including a polling frame, retransmission request frame, data frame, and the like, an error detection part 206 for detecting any error in the transmission frame using the error detection code added to the transmission frame, a frame header analysis part 207 for analyzing the transmission frame for its frame type and destination address, a frame order reconstruction part 208 for accumulating data frames, reading out those in order of frame number as instructed, and extracting data part for output, a retransmission control part 209 for controlling re
  • the data reception and transmission parts 205 and 204 are typically in a single modem 200. Here, as described in the foregoing, there no need to put those in the same modem as long as simultaneous data transmission and reception is prevented.
  • the polling period count part 201 forwards a command of polling transmission, at predetermined intervals, to the polling frame generation part 202 and the retransmission control part 209.
  • the polling frame generation part 202 generates a polling frame addressed to the adjoining relay transmitter for output to the error detection code addition part 203.
  • the polling frame is provided with an error detection code, and transmitted out of the data transmission part 204.
  • the transmission frame received by the data reception part 205 is determined if being normal or not by the error detection part 206. If any error is detected in the frame, the error detection part 206 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 207. If determined the analyzed frame as being a data frame addressed to its own terminal, the frame is accumulated in the frame order reconstruction part 208. The retransmission control part 209 then detects, after receiving a series of data, whether every data has been accumulated in the frame order reconstruction part 208. If every data frame is found therein, the retransmission control part 209 brings the frame order reconstruction part 208 to output the accumulated data frames in order of frame number. Here, the output is reception data.
  • the retransmission control part 209 calculates, based on the timing when the last command of polling transmission was inputted from the polling period count part 201, a length of time until the next polling transmission. The calculated time is compared with a value calculated by an equation of (the number of to-be-retransmitted frames + 1) ⁇ (the number of transfers among the transmitters) ⁇ (a time taken to transmit one frame) + ⁇ (a constant determined by the processing capability) .
  • the retransmission control part 209 controls the retransmission request frame generation part 210 to generate a retransmission request frame, which includes the frame number(s) of the not-yet-reached data frame(s).
  • generated retransmission request frame is herein addressed to the adjacent relay transmitter.
  • the generated retransmission request frame is added with an error detection code by the error detection code addition part 203, and is transmitted out of the data transmission part 204.
  • the retransmission control part 209 stops transmission of the retransmission request frame.
  • the transmitter on the transmission side 30 is provided with a data reception part 301 for demodulating a transmission wave on a transmission path, and generating a transmission frame including a polling frame, retransmission request frame, data frame, and the like, an error detection part 302 for detecting any error in the transmission frame using an error detection code added to the transmission frame, a frame header analysis part 303 for analyzing the transmission frame for its type and destination address, a transmission control part 304 for controlling other parts, a retransmission frame buffer 305 for accumulating a to-be-transmitted transmission frame, a transmission data buffer 306 for accumulating transmission data, a data frame generation part 307 for adding the data with a frame number, another error detection code, and a destination address, an error detection code addition part 308 for calculating and adding the error detection code in the transmission frame, a data transmission part 309 for demodulating the transmission frame for send-out onto the transmission path as another transmission wave, and a retransmission control part 310 for retransmission
  • the data reception and transmission parts 301 and 309 are typically in a single modem 300. Here, as described in the foregoing, there no need to put those in the same modem as long as simultaneous data transmission and reception is prevented.
  • the data reception part 301 receives a transmission frame.
  • the received transmission frame is determined if being normal or not by the error detection part 302. If any error is detected in the frame, the error detection part 302 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 303.
  • the frame header analysis part 303 informs the transmission control part 304 and the retransmission control part 310.
  • the retransmission control part 310 clears the retransmission frame buffer 305.
  • the transmission control part 304 controls data in the transmission data buffer 306 to be outputted by the predetermined number for the data frame generation part 307.
  • the data is then sequentially provided with a frame number.
  • the data is framed, and addressed to the adjacent relay transmitter.
  • the framed data is provided with an error detection code by the error detection code addition part 308. Then, the data is accumulated in the retransmission frame buffer 305, and transmitted out of the data transmission part 309.
  • the frame header analysis part 303 informs the retransmission control part 310, and also forwards the retransmission request frame to the retransmission control part 310.
  • the retransmission control part 310 extracts the frame number(s) in the received retransmission request frame, and then outputs the data frame(s) corresponding to the frame number(s) from the retransmission frame buffer 305 to the data transmission part 309. The outputted data is then transmitted out of the data transmission part 309.
  • FIG. 4 is a diagram showing a transfer sequence in the data transmission system of this embodiment.
  • each device is presumed to perform radio data transmission in the same frequency range. Also, presumably, a polling generated in the transmitter on the reception side in this system goes to a second relay transmitter and then a first before reaching the transmitter on the transmission side.
  • the transmitter on the transmission side transmits 1st to 7th data frames to the first relay transmitter.
  • a cross in the drawing shows that any error occurs in the data frame.
  • the crossed data frame is discarded by the transmitter on the reception side, the first relay transmitter, or the second relay transmitter.
  • the first relay transmitter stores the normally-received 1st, 2nd, 5th, 6th, and 7th data frames into its retransmission frame buffer as already described, and simultaneously, transmits those to the second relay transmitter.
  • the second relay transmitter then stores the normally-received 1st, 2nd, 5th, and 7th data frames into its retransmission frame buffer, and simultaneously, transmits those to the transmitter on the reception side.
  • the transmitter on the reception side stores the 1st, 2nd, 5th, and 7th data frames as already described into the frame order reconstruction part 208. Then, the retransmission control part 209 determines that the 3rd, 4th, and 6th data frames are missing.
  • the second relay transmitter does not have the 3rd, 4th, and 6th data frames stored in its retransmission frame buffer. Therefore, the retransmission request frame is forwarded to the first relay transmitter without any change.
  • the first relay transmitter has the 6th data frame stored in its retransmission frame buffer. Therefore, as described above, the 6th data frame is stored in the relay buffer. The frame number of the 6th data frame is then deleted from the retransmission request frame, and another retransmission request frame is generated to request retransmission of the 3rd and 4th data frames. Such generated retransmission request frame is transmitted to the transmitter on the transmission side.
  • the transmitter on the transmission side transmits the 3rd and 4th data frames to the first relay transmitter.
  • the first relay transmitter stores the 3rd and 4th data frames in its retransmission frame buffer, adds the 6th data frame to the 3rd and 4th data frames, and then transmits those data frames to the second relay transmitter.
  • the second relay transmitter stores the 3rd, 4th, and 6th data frames in its retransmission frame buffer, and simultaneously, transmits those to the transmitter on the reception side.
  • the transmitter on the reception side stores the normally-received 4th and 6th data frames into the frame order reconstruction part 208. Thereafter, the retransmission control part 209 determines that the 3rd data frame is missing.
  • the second relay transmitter has the 3rd data frame stored in its retransmission frame buffer. Therefore, the 3rd data frame is stored in the relay buffer.
  • the 3rd data frame is everything requested by the retransmission request frame, this is the end of transmission of the retransmission request frame. Thereafter, the 3rd data frame is transmitted from the second relay transmitter to the transmitter on the reception side.
  • the transmitter on the reception side stores the normally-received 3rd data frame in the frame order reconstruction part 208. Then, the retransmission control part 209 determines the data frame as being received, and then instructs the frame order reconstruction part 208 to output data. The frame order reconstruction part 208 then reads out the stored data frames in order of frame number for output.
  • the transmission order of the transmission frames is sequentially passed among the transmitters, and then data transmission and retransmission are performed. Thanks to this, even in a case where transmission on a data link affects transmission on another data link as does in a radio transmission path, relay transmission can be done with no problem. Further, retransmission can be efficiently achieved even on a transmission path where an error rate is high.
  • the number of relay transmitters in the data transmission system of this embodiment is two, that is, two-stage relay transmission is taken as an example.
  • this is not restrictive and may be M-stage relay transmission (M is a natural number) where the number of transmitters is M. If this is the case, the data transmission system of this embodiment is still effective in the same level.
  • a transmission path is presumably a radio transmission path.
  • a wired transmission path on which the transmitters are connected in a bus shape is also a possibility. If this is the case, the data transmission system of this embodiment is also still effective in the same level.
  • FIGS. 5 to 7 are diagrams showing the structure of a data transmission system according to a second embodiment of the present invention.
  • FIG. 5 shows the structure of a relay transmitter 50 located between transmitters on the transmission and reception sides 70 and 60 for increasing the distance for data transmission
  • FIG. 6 the structure of the transmitter on the reception side 60 for receiving data transmitted from the transmitter on the transmission side 70
  • FIG. 7 the structure of the data transmitter on the transmission side 70.
  • the transmitter on the reception side 60, transmitter on the transmission side 70, and relay transmitter 50 are connected to one another via transmission paths 40.
  • the data transmission system of the second embodiment is structurally almost similar to that of the first embodiment. Therefore, only the difference therebetween is described below.
  • the relay transmitter 50 is almost similar in structure to the relay transmitter 10 in FIG. 1, but additionally provided with a transfer valid period control part 501 and a transfer valid period addition part 502.
  • the transfer valid period control part 501 stores a transfer valid period, and decreases the period by 1 whenever a time taken for transmitting one transmission frame passes.
  • the transfer valid period addition part 502 information on such transfer valid period is added to the transmission frame.
  • the transmitter on the reception side 60 is almost similar in structure to the transmitter on the reception side 20 in FIG. 2, but additionally provided with a transfer valid period control part 601 and a transfer valid period addition part 602.
  • the transfer valid period control part 601 stores a transfer valid period, and decreases the period by 1 whenever a time taken for transmitting one frame.
  • the transfer valid period addition part 602 information on such transfer valid period is added on the transmission frame.
  • the transmitter on the transmission side 70 is almost similar in structure to the transmitter on the transmission side 30 in FIG. 3, but additionally provided with a transfer valid period control part 701 and a transfer valid period addition part 702.
  • the transfer valid period control part 701 stores a transfer valid period, and decreases the period by 1 whenever a time taken for transmitting one frame.
  • the transfer valid period addition part 702 information on such transfer valid period is added on the transmission frame.
  • the data reception part 101 receives a transmission frame.
  • the received transmission frame is determined as being normal or not by the error detection part 102. If any error is detected in the frame, the error detection part 102 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 103.
  • the frame header analysis part 103 decreases a transfer valid period in the frame by 1, and then stores information on the transfer valid period in the transfer valid period control part 501.
  • the frame header analysis part 103 also informs the relay control part 104 of the frame type of the analyzed.
  • the relay control part 104 clears the retransmission frame buffer 105 and the relay buffer 106.
  • the relay control part 104 also brings the destination address change part 107 to rewrite the polling frame to address to the adjacent transmitter on the transmission side, and to output the frame to the transfer valid period addition part 502.
  • the transfer valid period addition part 502 adds, to the polling frame, the information on the transfer valid period stored in the transfer valid period control part 501. Then, the polling frame is also added with an error detection code by the error detection code addition part 108, and is transmitted out of the data transmission part 109.
  • the relay control part 104 brings the destination address change part 107 to rewrite the data frame to address to the adjacent transmitter on the reception side. Also, the relay control part 104 brings the data frame to be accumulated in the retransmission frame buffer 105, while storing the data frame in the relay buffer 106.
  • the relay control part 104 controls, if detected reception of a series of data frames having been completed, the data frames in the relay buffer 106 to be forwarded to the transfer valid period addition part 502, and after the control, clears the relay buffer 106.
  • the transfer valid period addition part 502 adds the transfer valid period decreased by 1 to each corresponding data frame.
  • the transfer valid period is the one informed by the transfer valid period control part 501.
  • the data frames are also added each with an error detection code by the error detection code addition part 108, and are transmitted out of the data transmission part 109.
  • the relay control part 104 clears the relay buffer 106. Then, the relay control part 104 determines whether the retransmission frame buffer 105 has a data frame requested for retransmission. If found, the data frame is stored in the relay buffer 106.
  • the relay control part 104 also informs the retransmission request frame reconstruction part 110 of a frame number(s) found in the retransmission frame buffer 105.
  • the relay control part 104 controls the retransmission request frame reconstruction part 110 to remove, out of the retransmission request frame received from the frame header analysis part 103, any frame number(s) already stored in the retransmission frame buffer 105, and forwards the retransmission request frame to the destination address change part 107.
  • the relay control part 104 brings the destination address change part 107 to rewrite the retransmission request frame to address to the transmitter on the transmission side, and then to output the frame to the transfer valid period addition part 502.
  • the transfer valid period addition part 502 adds, to the received retransmission request frame, the transfer valid period information informed by the transfer valid period control part 501. Then, the retransmission request frame is also added with an error detection code by the error detection code addition part 108, and is transmitted out of the data transmission part 109.
  • the transfer valid period control part 501 decreases the transfer valid period stored therein by 1 whenever a time taken to transmit one transmission frame passes.
  • the transfer valid period control part 501 informs the relay control part 104.
  • the informed relay control part 104 then controls other parts to stop transmission of the transmission frame.
  • the polling period count part 201 forwards a command of polling transmission at predetermined intervals to the polling frame generation part 202.
  • the polling period count part 201 also stores information on transfer valid period in the transfer valid period control part 601.
  • the information is a value obtained by dividing a polling period by a time taken to transmit one transmission frame.
  • the transfer valid period control part 601 informs the transfer valid period addition part 602 of the stored information.
  • the polling frame generation part 202 When receiving the command of polling transmission, the polling frame generation part 202 generates a polling frame addressed to the adjacent relay transmitter, and forwards the polling frame to the transfer valid period addition part 602. To the received polling frame, the transfer valid period addition part 602 then adds the transfer valid period information received from the transfer valid period control part 601. The polling frame then is additionally provided with an error detection code by the error detection code addition part 203, and is transmitted out of the data transmission part 204.
  • the data reception part 205 receives a transmission frame from the adjacent transmitter.
  • the transmission frame is then determined as being normal or not by the error detection part 206. If any error is detected in the frame, the error detection part 206 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 207.
  • the frame header analysis part 207 decreases a transfer valid period in the frame by 1, and stores information on the transfer valid period in the transfer valid period control part 601. The stored transfer valid period information is informed to the transfer valid period addition part 602. The frame header analysis part 207 then informs the retransmission control part 209 of the frame having arrived, and then accumulates the frame in the frame order reconstruction part 208.
  • the retransmission control part 209 detects, after receiving a series of data, whether every data has been accumulated in the frame order reconstruction part 208. If every data frame is found therein, the retransmission control part 209 brings the frame order reconstruction part 208 to output data in order of frame number. Here, the output is reception data.
  • the retransmission control part 209 brings the retransmission request frame generation part 210 to generate a retransmission request frame including a frame number(s) of the not-yet-reached data frame(s), and to forward thus generated retransmission request frame to the transfer valid period addition part 602.
  • the retransmission request frame is herein addressed to the adjacent relay transmitter.
  • the transfer valid period addition part 602 adds the transfer valid period information received from the transfer valid period control part 601.
  • the retransmission request frame is then added with an error detection code by the error detection code addition part 203, and is transmitted out of the data transmission part 204.
  • the transfer valid period control part 601 decreases the transfer valid period stored therein by 1 whenever a time taken to transmit one transmission frame passes.
  • the transfer valid period control part 601 informs the retransmission control part 209.
  • the retransmission control part 209 then controls other parts to stop transmission of the transmission frame.
  • the data reception part 301 receives a transmission frame.
  • the error detection part 302 determines the transmission frame as being normal or not. If any error is detected in the frame, the error detection part 302 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 303.
  • the frame header analysis part 303 decreases a transfer valid period in the frame by 1, and then stores information on the transfer valid period in the transfer valid period control part 701. The stored transfer valid period information is informed to the transfer valid period addition part 702.
  • the frame header analysis part 303 also informs the transmission control part 304 of the polling frame having arrived.
  • the transmission control part 304 informed of the poling frame having arrived then clears the retransmission frame buffer 305, and reads data from the transmission data buffer 306 by the predetermined number of frames.
  • the read data is then sequentially provided with a frame number by the data frame generation part 307, thus the data is framed, and addressed to the adjacent relay transmitter.
  • the transmission control part 304 stores the framed data in the retransmission frame buffer 305, and simultaneously forwards the framed data to the transfer valid period addition part 702.
  • the transfer valid period addition part 702 then adds the received transfer valid period information to the data frames.
  • the data frames are then additionally each provided with an error detection code by an error detection code addition part 308, and transmitted out of a data transmission part 309.
  • the frame header analysis part 303 decreases a transfer valid period in the frame by 1, and then stores information on the transfer valid period in the transfer valid period control part 701. The stored transfer valid period information is then informed to the transfer valid period addition part 702.
  • the frame header analysis part 303 informs the retransmission control part 310 that the retransmission request frame has arrived.
  • a retransmission control part 310 After being informed of the retransmission request frame having arrived, a retransmission control part 310 extracts the frame number(s) in the received retransmission request frame. Thereafter, the retransmission control part 310 reads out the data frame(s) corresponding to the frame number(s) from the retransmission frame buffer 305 for output to the transfer valid period addition part 702.
  • the transfer valid period addition part 702 adds the transfer valid period information received from the transfer valid period control part 702.
  • the retransmission request frame then additionally provided with an error detection code by the error detection code addition part 308, and is transmitted out of the data transmission part 309.
  • the transfer valid period control part 701 decreases the transfer valid period information stored therein whenever a time taken to transmit one transmission frame passes.
  • the transfer valid period control part 701 informs the retransmission control part 310. After being informed, the retransmission control part 310 controls other parts to stop transmission of the transmission frame.
  • FIG. 8 is a diagram showing a transfer sequence in the data transmission system of this embodiment.
  • a first to a third data links are presumed to perform radio data transmission in the same frequency range.
  • a polling generated in the transmitter on the reception side in this system goes to a second relay transmitter and then a first before reaching the transmitter on the transmission side.
  • bracketed figures such as (1) in the drawing denote frame numbers, while those such as [1] denote a transfer valid period. The transfer valid period is decreased by 1 whenever a transmission frame is relayed or transmitted.
  • the transmitter on the transmission side transmits 1st to 7th data frames to the first relay transmitter.
  • a cross in the drawing shows that any error occurs in the data frame.
  • the crossed 1st and 2nd data frames are discarded by the first relay transmitter.
  • the first relay transmitter stores the normally-received 3rd, 4th, 5th, 6th, and 7th data frames into its retransmission frame buffer, and simultaneously, transmits those to the second relay transmitter.
  • the second relay transmitter then stores the normally-received 5th and 7th data frames into the retransmission frame buffer, and simultaneously, transmits those to the transmitter on the reception side.
  • the transmitter on the reception side stores the 5th and 7th data frames into the frame order reconstruction part. Then, an instruction is made by the retransmission control part to generate a retransmission request frame asking for retransmission of the missing data frames of 1st, 2nd, 3rd, 4th, and 6th.
  • the generated retransmission request frame is transmitted to the second relay transmitter.
  • the second relay transmitter does not have the 1st, 2nd, 3rd, 4th, and 6th data frames stored in its retransmission frame buffer. Therefore, the retransmission request frame is forwarded to the first relay transmitter without any change.
  • the first relay transmitter has the 3rd, 4th, and 6th data frames stored in its retransmission frame buffer. Therefore, the 3rd, 4th, and 6th data frames are stored in the relay buffer. Thereafter, a retransmission request frame asking for retransmission of data frames of 1st and 2nd is generated, and is transmitted to the transmitter on the transmission side.
  • the transmitter on the transmission side transmits the 1st and 2nd data frames to the first relay transmitter.
  • the first relay transmitter stores the 1st and 2nd data frames in its retransmission frame buffer, and simultaneously in the relay buffer.
  • the first relay transmitter transmits, to the second relay transmitter, the 1st and 2nd data frames together with the 3rd, 4th, and 6th data frames in the relay buffer.
  • the second relay transmitter stores the normally-stored 2nd data frame in its retransmission frame buffer, and simultaneously transmits that to the transmitter on the reception side.
  • the transmitter on the reception side stores the normally-stored 2nd data frame in the frame order reconstruction part. Moreover, an instruction is made by the retransmission control part to generate a retransmission request frame asking for retransmission of the missing data frames of 1st, 3rd, 4th, and 6th. The generated retransmission request frame is transmitted to the second relay transmitter.
  • the second relay transmitter does not have the 1st, 3rd, 4th, and 6th data frames stored in its retransmission frame buffer. Therefore, the retransmission request frame is forwarded to the first relay transmitter without any change.
  • the first relay transmitter has the 1st, 3rd, 4th, and 6th data frames stored in its retransmission frame buffer. Therefore, the 1st, 3rd, 4th, and 6th data frames are stored in the relay buffer. Herein, since every data frame requested for retransmission is found in the retransmission frame buffer, this is the end of transmission of the retransmission request frame. Thereafter, the 1st, 3rd, 4th, and 6th data frames are transmitted to the second relay transmitter.
  • the second relay transmitter stores the normally-received 1st, 3rd, and 6th data frames in its retransmission frame buffer, and simultaneously stores those in the relay buffer. Then, the 1st frame in the relay buffer is transmitted to the transmitter on the reception side. Here, this transmission result in the transfer valid period in the second relay transmitter being smaller than 0. Thus, this is the end of the transmission of the data frame.
  • the transmitter on the reception side transmits another polling as a polling period has passed since the last polling frame's transmission.
  • the transmission order of the transmission frames is sequentially passed among the transmitters, and then data transmission and retransmission are performed. Further, even if transmission takes time due to erroneous transmission, each of those transmitters can know when another polling comes next. Thanks to this, even in a case where transmission on a data link affects transmission on another data link as does in a radio transmission path, relay transmission can be done with no collision.
  • the transfer valid period information is an integer, being a unit of time taken to transmit one transmission frame.
  • this is not restrictive, and may be an actual time such as a second. If this is the case, the transfer valid period is not divided by 1 but by an actual time taken to transfer one transmission frame at the time when stored in the transfer valid period control part.
  • a transmission path is presumably a radio transmission path.
  • a wired transmission path on which the transmitters are connected in a bus shape is also a possibility. If this is the case, the data transmission system of this embodiment is also still effective in the same level.
  • the number of relay transmitters in the data transmission system of this embodiment is two, that is, two-stage relay transmission is taken as an example.
  • this is not restrictive and may be M-stage relay transmission (M is a natural number) where the number of transmitters is M. If this is the case, the data transmission system of this embodiment is still effective in the same level.
  • FIGS. 9 to 11 are diagrams showing the structure of a data transmission system according to a third embodiment of the present invention.
  • the data transmission system of the third embodiment includes a transmission path 41 being a radio transmission path, a transmitter on the reception side 61 for receiving data by radio via the transmission path 41 for output, a transmitter on the transmission side 71 for transmitting data by radio to the transmitter on the reception side 61, and a relay transmitter 51 located between transmitters on the transmission and reception sides 71 and 61 for increasing the distance for data transmission.
  • the data transmission system of the third embodiment is structurally almost similar to that of the second embodiment. Therefore, only the difference therebetween is described below.
  • the relay transmitter 51 does not include the data reception and transmission parts 105 and 109.
  • a radio reception part 901 for demodulating a transmission wave on the transmission path 41 so as to generate a transmission frame including data frame, polling frame, retransmission request frame, and the like, and a radio transmission part 902 for modulating a data frame for send-out onto the transmission path as another transmission wave.
  • the radio reception and transmission parts 901 and 902 are typically in a single modem 900. Here, as described in the foregoing, there no need to put those in the same modem as long as simultaneous data transmission and reception is prevented.
  • the relay transmitter 51 further includes an antenna control part 903 which controls switching of a directional antenna according to information provided by the radio transmission part 902 and the transfer valid period addition part 502, an antenna switching part 904 for performing antenna switching under the control of the antenna control part 903, and directional antennas 906 and 907 of a type performing radio transmission/reception only in a specific direction.
  • a radio signal from the directional antennas 906 and 907 goes to directional antennas 905 and 908, respectively.
  • the transmitter on the reception side 61 does not include the data reception and transmission parts 205 and 204.
  • the radio reception and transmission parts 1002 and 1001 are typically in a single modem 1000.
  • the transmitter on the transmission side 71 does not include the data reception and transmission parts 301 and 309.
  • a radio reception part 1101 for demodulating a transmission wave on the transmission path 41 so as to generate a transmission frame including data frame, polling frame, retransmission request frame, and the like, and a radio transmission part 1102 for modulating a data frame for send-out onto the transmission path as another transmission wave.
  • the radio reception and transmission parts 1101 and 1102 are typically in a single modem 1100. Here, as described in the foregoing, there no need to put those in the same modem as long as simultaneous data transmission and reception is prevented.
  • the radio reception part 901 receives a transmission frame.
  • the received transmission frame is determined as being normal or not by the error detection part 102. If any error is detected in the frame, the error detection part 102 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 103.
  • the frame header analysis part 103 decreases a transfer valid period stored therein by 1, and stores information on the transfer valid period in the transfer valid period control part 501.
  • the frame header analysis part 103 informs the frame type of the analyzed to the relay control part 104.
  • the relay control part 104 clears the retransmission frame buffer 105 and the relay buffer 106.
  • the relay control part 104 also brings the destination address change part 107 to rewrite the polling frame to address to the adjacent transmitter, and to output to the transfer valid period addition part 502.
  • the transfer valid period addition part 502 adds the transfer valid period information stored in the transfer valid period control part 501.
  • the polling frame is then additionally provided with an error detection code by the error detection code addition part 108.
  • the antenna control part 903 controls the antenna switching part 904 to select an antenna adjusted in the direction where the transmitter for transmitting the frame is located. Under such control, the antenna switching part 904 performs antenna switching. Thereafter, the radio transmission part 902 transmits the polling frame.
  • the antenna control part 903 internally has a timer, which timeouts once the transfer valid period provided by the transfer valid period addition part 502 passed. when the timer timeouts, the antenna control part 903 controls the antenna switching part 904 so that the antenna is adjusted back to the direction where the transmitter on the reception side is located. Under such control, the antenna switching part 904 performs antenna switching.
  • the relay control part 104 brings the destination address part 107 to rewrite the data frame to address to the transmitter on the reception side. Then, the relay control part 104 accumulates the data frame in the retransmission frame buffer 105, while storing the data frame in the relay buffer 106.
  • the relay control part 104 also controls, if detected reception of a series of data frames having been completed, the data frames in the relay buffer 106 to be forwarded to the transfer valid period addition part 502. After completion of such control, the relay buffer 106 is cleared.
  • the transfer valid period addition part 502 adds the transfer valid period decreased by 1 to each corresponding data frame.
  • the transfer valid period is the one informed by the transfer valid period control part 501.
  • the data frames are also added each with an error detection code by the error detection code addition part 108.
  • the antenna control part 903 controls the antenna switching part 904 to select an antenna adjusted in the direction where the transmitter for transmitting the frame is located. Under such control, the antenna switching part 904 performs antenna switching. Thereafter, the radio transmission part 902 transmits the data frame.
  • the antenna control part 903 has, as already described, the timer which timeouts once the transfer valid period passed. When the timer timeouts, the antenna control part 903 controls the antenna switching part 904 so that the antenna is adjusted back to the direction where the transmitter on the reception side is located. Under such control, the antenna switching part 904 performs antenna switching.
  • the relay control part 104 clears the relay buffer 106, and checks whether a data frame(s) requested for retransmission is found in the retransmission frame buffer 105. If found, the data frame(s) is stored in the relay buffer 106.
  • the relay control part 104 also informs the retransmission request frame reconstruction part 110 of the data frame(s) by frame number found in the retransmission frame buffer 105.
  • the relay control part 104 controls the retransmission request frame reconstruction part 110 to remove, out of the retransmission request frame, any frame number(s) already stored in the retransmission frame buffer 105, and forwards the retransmission request frame to the destination address change part 107.
  • the relay control part 104 controls the destination address change part 107 to rewrite the retransmission request frame to address to the transmitter on the transmission side, and then to output the frame to the transfer valid period addition part 502.
  • the transfer valid period addition part 502 adds the transfer valid period information provided by the transfer valid period control part 501.
  • the retransmission request frame is then additionally provided with an error detection code by the error detection code addition part 108.
  • the antenna control part 903 controls the antenna switching part 904 to select an antenna adjusted in the direction where the transmitter for transmitting the frame is located. Under such control, the antenna switching part 904 performs antenna switching. Thereafter, the radio transmission part 902 transmits the polling frame.
  • the antenna control part 903 internally has, as already described, the timer which timeouts once the transfer valid period passed. When the timer timeouts, the antenna control part 903 controls the antenna switching part 904 so that the antenna is adjusted back to the direction where the transmitter on the reception side is located. Under such control, the antenna switching part 904 performs antenna switching.
  • the transfer valid period control part 501 decreases the transfer valid period stored therein by 1 whenever a time taken to transmit one transmission frame passes.
  • the transfer valid period control part 501 informs the relay control part 104.
  • the informed relay control part 104 then controls other parts to stop transmission of the transmission frame.
  • the polling period count part 201 forwards a command of polling transmission at predetermined intervals to the polling frame generation part 202.
  • the polling period count part 201 also stores, in the transfer valid period control part 601 as the transfer valid period information, a value obtained by dividing the polling period by a time taken to transmit one transmission frame.
  • the polling frame generation part 202 When receiving the command of polling transmission, the polling frame generation part 202 generates a polling frame addressed to the adjacent relay transmitter, and forwards the polling frame to the transfer valid period addition part 602. To the received polling frame, the transfer valid period addition part 602 then adds the transfer valid period information received from the transfer valid period control part 601. The polling frame then is additionally provided with an error detection code by the error detection code addition part 203, and is transmitted out of the radio transmission part 1001.
  • the radio reception part 1002 receives a transmission frame.
  • the received transmission frame is determined as being normal or not by the error detection part 206. If any error is detected in the frame, the error detection part 206 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 207.
  • the frame header analysis part 207 decreases a transfer valid period in the frame by 1, and then stores information on the transfer valid period in the transfer valid period control part 601.
  • the frame header analysis part 207 also informs the retransmission control part 209 that the frame has arrived, and the frame is accumulated in the frame order reconstruction part 208.
  • the retransmission control part 209 detects, after receiving a series of data, whether every data frame has been accumulated in the frame order reconstruction part 208. If every data frame is found therein, the retransmission control part 209 brings the frame order reconstruction part 208 to output the accumulated data frames in order of frame number. Here, the output is reception data.
  • the retransmission control part 209 brings the retransmission request frame generation part 210 to generate a retransmission request frame including a frame number(s) of the not-yet-reached data frame(s), and to output thus generated retransmission request to the transfer valid period addition part 602.
  • the generated retransmission request frame is addressed to the adjacent relay transmitter.
  • the transfer valid period addition part 602 adds the transfer valid period information stored in the transfer valid period control part 601.
  • the retransmission request frame is then added with an error detection code by the error detection code addition part 203, and is transmitted out of the radio transmission part 1001.
  • the transfer valid period control part 601 decreases the transfer valid period stored therein by 1 whenever a time taken to transmit one transmission frame passes.
  • the transfer valid period control part 601 informs the retransmission control part 209.
  • the informed retransmission control part 209 then controls other parts to stop transmission of the transmission frame.
  • the radio reception part 1101 receives a transmission frame.
  • the error detection part 302 determines the transmission frame as being normal or not. If any error is detected in the frame, the error detection part 302 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 303.
  • the frame header analysis part 303 decreases a transfer valid period in the frame by 1, and stores information on the transfer valid period in the transfer valid period control part 701. The frame header analysis part 303 then informs the transmission control part 304 of the polling frame having arrived.
  • the transmission control part 304 clears the retransmission frame buffer 305, and then reads the transmission data buffer 306 for only by the predetermined number of frames. The read data is then sequentially provided with a frame number by the data frame generation part 307, thus the data is framed, and addressed to the adjacent relay transmitter.
  • the transmission control part 304 stores the framed data in the retransmission frame buffer 305, and simultaneously forwards the framed data to the transfer valid period addition part 702.
  • the transfer valid period addition part 702 then adds the received transfer valid period information to the data frames.
  • the data frames are then additionally each provided with an error detection code by the error detection code addition part 308, and transmitted out of the radio transmission part 1102.
  • the frame header analysis part 303 decreases a transfer valid period in the frame by 1, and then stores the information in the transfer valid period control part 701.
  • the frame header analysis part 303 also informs the relay control part 310 that the retransmission request frame has arrived.
  • the retransmission control part 310 extracts the frame number(s) in the received retransmission request frame, and then reads out the data frame(s) corresponding to the frame number(s) from the retransmission frame buffer 305 for output to the transfer valid period addition part 702.
  • the data frames are also added each with the transfer valid period information stored in the transfer valid period control part 701 by the transfer valid period addition part 702.
  • the data frames are then additionally each provided with an error detection code by the error detection code addition part 308, and are transmitted out of the radio transmission part 1102.
  • the transfer valid period control part 701 decreases the transfer valid period stored therein by 1 whenever a time taken to transmit one transmission frame passes.
  • the transfer valid period control part 701 informs the retransmission control part 310.
  • the informed retransmission control part 310 then controls other parts to stop transmission of the transmission frame.
  • FIG. 12 is a diagram showing a transfer sequence in the data transmission system of this embodiment.
  • a first to a third data links are presumed to perform radio data transmission in the same frequency range.
  • antennas provided to the first and second relay transmitters are both adjusted in a direction where the transmitter on the reception side is located.
  • bracketed figures such as (1) in the drawing denote frame numbers, while those such as [1] denote a transfer valid period. The transfer valid period is decreased by 1 whenever a transmission frame is relayed or transmitted.
  • a polling generated in the transmitter on the reception side goes to the second relay transmitter, and then the first, before reaching the transmitter on the transmission side. Once received the polling, the first and second relay transmitters activate
  • the transmitter on the transmission side transmits 1st to 7th data frames to the first relay transmitter.
  • a cross in the drawing shows that any error occurs in the data frame.
  • the crossed data frame is discarded by the first relay transmitter.
  • the first relay transmitter stores the normally-received 3rd, 4th, 5th, 6th, and 7th data frames into its retransmission frame buffer, and simultaneously, transmits those to the second relay transmitter.
  • the timer Ta1 is reset, and thus the antenna is adjusted back to the direction where the transmitter on the reception side is located. This timing is indicated by D in the drawing.
  • the timer Ta1 may be structured to update the transfer valid period information whenever another comes.
  • the second relay transmitter discards those.
  • the antenna is adjusted back to the direction where the transmitter on the reception side is located when the timer Ta2 timeouts. The timing is indicated by B in the drawing.
  • the antennas can be precisely adjusted by using the timer in the antenna control part 903.
  • the antenna in the respective relay transmitters is adjusted back to the transmitter on the reception side, without fail, when a new polling comes, therefore reception of the polling frame is assuredly done.
  • the antenna switching part 904 performs antenna switching with respect to two directional antennas of 906 and 907.
  • the number of the directional antenna may be only 1, and the antenna control part 903 may direct the antenna.
  • the antenna control part 903 rotates the antenna so as to change its direction.
  • the antenna may be an adaptive array antenna, and the antenna control part 903 may weigh differently a signal coming from each antenna device to change its direction.
  • the transfer valid period information is an integer, being a unit of time taken to transmit one transmission frame.
  • this is not restrictive, and may be an actual time such as a second. If this is the case, the transfer valid period is not divided by 1 but by an actual time taken to transfer one transmission frame at the time when stored in the transfer valid period control part.
  • the number of relay transmitters in the data transmission system of this embodiment is two, that is, two-stage relay transmission is taken as an example.
  • this is not restrictive and may be M-stage relay transmission (M is a natural number) where the number of transmitters is M. If this is the case, the data transmission system of this embodiment is still effective in the same level.
  • FIG. 13 is a diagram showing the structure of a data transmission system according to a fourth embodiment of the present invention.
  • the data transmission system of the fourth embodiment includes the transmission path 41 being a radio transmission path, the transmitter on the reception side 61 for receiving data by radio via the transmission path 41 for output, the transmitter on the transmission side 71 for transmitting data by radio to the transmitter on the reception side 61, and a relay transmitter 52 located between transmitters on the transmission and reception sides 71 and 61 for increasing the distance for data transmission.
  • the data transmission system of the third embodiment is structurally almost similar to that of the third embodiment. Therefore, only the difference therebetween is described below.
  • the relay transmitter 52 includes a radio reception part 1401 capable of switching among several frequency channels, and a radio transmission part 1402.
  • the radio reception and transmission parts 1401 and 1402 are typically in the
  • the relay transmitter 52 further includes a frequency channel control part 1403 for controlling switching of frequency channels according to information provided by the radio transmission part 1402 and the transfer valid period addition part 502.
  • the transmitter on the reception side 61 is structurally identical to that in FIG. 10, and the transmitter on the transmission side 71 to that in FIG. 11.
  • the data reception part 1401 receives a transmission frame.
  • the received transmission frame is determined as being normal or not by the error detection part 102. If any error is detected in the frame, the error detection part 102 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 103.
  • the frame header analysis part 103 decreases a transfer valid period in the frame by 1, and then stores information on the transfer valid period in the transfer valid period control part 501.
  • the frame header analysis part 103 also informs the relay control part 104 of the frame type of the analyzed.
  • the relay control part 104 clears the retransmission frame buffer 105 and the relay buffer 106.
  • the relay control part 104 also brings the destination address change part 107 to rewrite the polling frame to address to the adjacent transmitter on the transmission side, and to output the frame to the transfer valid period addition part 502.
  • the transfer valid period addition part 502 adds, to the polling frame, the information on the transfer valid period stored in the transfer valid period control part 501. Then, the polling frame is also added with an error detection code by the error detection code addition part 108.
  • the frequency channel control part 1403 controls the radio reception and transmission parts 1401 and 1402 to be in a frequency channel for communications with the adjacent transmitter on the transmission side. Then, the radio transmission part 1402 transmits the polling frame.
  • the frequency channel control part 1403 internally has a timer, which timeouts once the transfer valid period received from the transfer valid period addition part 502 passed.
  • the frequency channel control part 1403 controls the radio reception and transmission parts 1401 and 1402 so as to be again in a frequency channel used for communications with the transmitter on the reception side.
  • the relay control part 104 brings the destination address change part 107 to rewrite the data frame to address to the adjacent transmitter on the reception side. Also, the relay control part 104 accumulates the data frame in the retransmission frame buffer 105, while storing the data frame in the relay buffer 106.
  • the relay control part 104 controls, if detected reception of a series of data frames having been completed, the data frames in the relay buffer 106 to be forwarded to the transfer valid period addition part 502, and after the control, clears the relay buffer 106.
  • the transfer valid period addition part 502 adds the transfer valid period decreased by 1 to each corresponding data frame. Then, the data frames are also added each with an error detection code by the error detection code addition part 108.
  • the frequency channel control part 1403 sets the radio reception and transmission parts 1401 and 1402 so as to be in a frequency channel for communications with the transmitter on the transmission side, which transmits the frames. Then, the radio transmission part 1402 transmits the data frames.
  • the frequency channel control part 1403 internally has the timer, which timeouts once the transfer valid period passed.
  • the frequency channel control part 1403 controls the radio reception and transmission parts 1401 and 1402 to be again in a frequency channel used in communications with the transmitter on the reception side.
  • the relay control part 104 clears the relay buffer 106. Then, the relay control part 104 determines whether the retransmission frame buffer 105 has a data frame requested for retransmission. If found, the data frame is stored in the relay buffer 106.
  • the relay control part 104 also informs the retransmission request frame reconstruction part 110 of a frame number(s) found in the retransmission frame buffer 105.
  • the relay control part 104 controls the retransmission request frame reconstruction part 110 to remove, out of the retransmission request frame received from the frame header analysis part 103, any frame number(s) already stored in the retransmission frame buffer 105, and forwards the retransmission request frame to the destination address change part 107.
  • the relay control part 104 brings the destination address change part 107 to rewrite the retransmission request frame to address to the transmitter on the transmission side, and then to output the frame to the transfer valid period addition part 502.
  • the transfer valid period addition part 502 adds, to the received retransmission request frame, the transfer valid period information informed by the transfer valid period control part 501. Then, the retransmission request frame is also added with an error detection code by the error detection code addition part 108.
  • the frequency channel control part 1403 controls the radio reception and transmission parts 1401 and 1402 to be in a frequency channel for communications with the transmitter on the transmission side, which transmits the frame. Then, the radio transmission part 1402 transmits the retransmission request frame.
  • the frequency channel control part 1403 internally has the timer, which timeouts once the transfer valid period passed.
  • the frequency channel control part 1403 controls the radio reception and transmission parts 1401 and 1402 to be again in a frequency channel used for communications with the transmitter on the reception side.
  • the transfer valid period control part 501 decreases the transfer valid period stored therein by 1 whenever a time taken to transmit one transmission frame passes.
  • the transfer valid period control part 501 informs the relay control part 104.
  • the informed relay control part 104 then controls other parts to stop transmission of the transmission frame.
  • the transmitters on the reception and transmission sides 61 and 71 both operate in the same manner as in the third embodiment, and therefore is not described again.
  • FIG. 14 is a diagram showing a transfer sequence in the data transmission system of this embodiment.
  • data links are presumed to perform radio data transmission in each different frequency range, i.e., a first data link in channel 1, a second data link in channel 2, and a third data link in channel 3. This is typically done to prevent those data links from sharing the same frequency range as disturbance waves emitted from a wave source (e.g., microwave oven). Such disturbance waves disturb radio data transmission.
  • a wave source e.g., microwave oven
  • a wave source emitting a disturbance wave in the same frequency range as the channel 3 is in the vicinity of the first relay transmitter.
  • the first relay transmitter may have some difficulties to receive waves from the second relay transmitter or the transmitter on the transmission side with the channel 3. This is because, a disturbance wave emitted by a neighboring wave source generally intense but a wave coming from the transmitters being weak as came across the long distance. Therefore, such disturbance wave is quite likely to disturb data reception.
  • the second relay transmitter may have some difficulties to receive waves from the first relay transmitter or the transmitter on the reception side with the channel 1. If this is the case, setting the frequency channels for the data links as in FIG. 14 is a solution. With such setting, signal reception among transmitters can be satisfactorily done without being disturbed by the disturbance waves from the source.
  • a polling generated in the transmitter on the reception side goes to the second relay transmitter, and then the first, before reaching the transmitter on the transmission side.
  • the first and second relay transmitters activate the timers Ta1 and Ta2, respectively, based on transfer valid period information included in the polling.
  • Those timers Ta1 and Ta2 are respectively provided in an frequency control part of the first and second relay transmitters, and timeout after the transfer valid period passed.
  • the frequency control part in the first relay transmitter switches its channel to channel 1
  • the frequency control part in the second relay transmitter switches its channel to channel 2.
  • the switching timing is indicated by A and C in the drawing.
  • the transmitter on the transmission side transmits 1st to 7th data frames to the first relay transmitter.
  • a cross in the drawing shows that any error occurs in the data frame.
  • the crossed data frame is discarded by the first relay transmitter.
  • the first relay transmitter stores the normally-received 3rd, 4th, 5th, 6th, and 7th data frames into its retransmission frame buffer, and simultaneously, transmits those to the second relay transmitter.
  • the timer Ta1 is reset, and thus the channel is put back to channel 2. This timing is indicated by D in the drawing.
  • the timer Ta1 may be structured not to be reset, and update the transfer valid period information whenever another comes.
  • every data frame provided by the first relay transmitter is found erroneous.
  • the second relay transmitter discards those.
  • the channel is put back to channel 3 when the timer Ta2 timeouts. The timing is indicated by B in the drawing.
  • the channels can be precisely controlled by using the timer in the frequency control part 1403.
  • the channel in the respective relay transmitters is put back to the one used for communications with the transmitter on the reception side, without fail, when a new polling comes, therefore reception of the polling frame is assuredly done.
  • the radio reception and transmission parts 1401 and 1402 are exemplarily in a single modem 1400, and channels are concurrently switched.
  • the channel in each relay transmitter has to be put back to the channel used for communications with the transmitter on the reception side when the timer timeouts. In this manner, the polling frame can be assuredly received as described above.
  • the transfer valid period information is an integer, being a unit of time taken to transmit one transmission frame.
  • this is not restrictive, and may be an actual time such as a second. If this is the case, the transfer valid period is not divided by 1 but by an actual time taken to transfer one transmission frame at the time when stored in the transfer valid period control part.
  • the number of relay transmitters in the data transmission system of this embodiment is two, that is, two-stage relay transmission is taken as an example.
  • this is not restrictive and may be M-stage relay transmission (M is a natural number) where the number of transmitters is M. If this is the case, the data transmission system of this embodiment is still effective in the same level.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Radio Relay Systems (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Detection And Prevention Of Errors In Transmission (AREA)
  • Communication Control (AREA)
EP00123380A 1999-11-01 2000-10-31 Verfahren und System zur Relaisdatenwiederübertragung Withdrawn EP1096719A3 (de)

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CN107211261A (zh) * 2015-02-04 2017-09-26 瑞典爱立信有限公司 用于无线通信网络中的连接建立的方法和装置
CN107211261B (zh) * 2015-02-04 2021-04-09 瑞典爱立信有限公司 用于无线通信网络中的连接建立的方法和装置

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